Last data update: Sep 23, 2024. (Total: 47723 publications since 2009)
Records 1-3 (of 3 Records) |
Query Trace: Dougherty HN [original query] |
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Methane emissions and airflow patterns along longwall faces and through bleeder ventilation systems
Krog RB , Schatzel SJ , Dougherty HN . Int J Min Miner Eng 2014 5 (4) 328-349 The National Institute for Occupational Safety and Health (NIOSH) conducted an investigation of longwall face and bleeder ventilation systems using tracer gas experiments and computer network ventilation. The condition of gateroad entries, along with the caved material's permeability and porosity changes as the longwall face advances, determine the resistance of the airflow pathways within the longwall's worked-out area of the bleeder system. A series of field evaluations were conducted on a four-panel longwall district. Tracer gas was released at the mouth of the longwall section or on the longwall face and sampled at various locations in the gateroads inby the shield line. Measurements of arrival times and concentrations defined airflow/gas movements for the active/completed panels and the bleeder system, providing real field data to delineate these pathways. Results showed a sustained ability of the bleeder system to ventilate the longwall tailgate corner as the panels retreated. |
A new methane control and prediction software suite for longwall mines
Dougherty HN , Karacan CO . Comput Geosci 2011 37 (9) 1490-1500 This paper presents technical and application aspects of a new software suite, MCP (Methane Control and Prediction), developed for addressing some of the methane and methane control issues in longwall coal mines. The software suite consists of dynamic link library (DLL) extensions to MS-AccessTM, written in C++. In order to create the DLLs, various statistical, mathematical approaches, prediction and classification artificial neural network (ANN) methods were used. The current version of MCP suite (version 1.3) discussed in this paper has four separate modules that (a) predict the dynamic elastic properties of coal-measure rocks, (b) predict ventilation emissions from longwall mines, (c) determine the type of degasification system that needs to be utilized for given situations and (d) assess the production performance of gob gas ventholes that are used to extract methane from longwall gobs. These modules can be used with the data from basic logs, mining, longwall panel, productivity, and coal bed characteristics. The applications of these modules separately or in combination for methane capture and control related problems will help improve the safety of mines. The software suite's version 1.3 is discussed in this paper. Currently, it's new version 2.0 is available and can be downloaded from http://www.cdc.gov/niosh/mining/products/product180.htm free of charge. The models discussed in this paper can be found under "ancillary models" and under "methane prediction models" for specific U.S. conditions in the new version. |
Reservoir diagnosis of longwall gobs through drawdown tests and decline curve analyses of gob gas venthole productions
Dougherty HN , Karacan CO , Goodman GVR . Int J Rock Mech Min Sci 2010 47 (5) 851-857 During longwall mining, fracturing and relaxation in the gob creates new and highly permeable flow paths. Methane inflow from the gob into the mining environment is influenced by the magnitude of fracturing and the extent to which the fractures stay open during mining. Singh and Kendorski [1] evaluated the disturbance of rock strata resulting from mining and described a caved zone that extends from the mining level to 3–6 times the seam thickness, a fractured zone that extends from the mining level to 30–58 times the seam thickness, and a bending zone where there is no change in permeability that extends from 30 times the seam thickness to 50 ft below ground surface. The characteristics of fracturing and the subsidence of overburden were revealed through predictive techniques and field studies [2], [3], [4], [5], [6]. It was concluded that rock failure leading to increased hydraulic conductivity in the gob was initiated by high compressive stresses ahead of the face with the fractures subsequently opened by tensile stresses behind the face [7]. | Gas, particularly methane that is contained within the gob, will be released over time as mining progresses and is a big contributor to ventilation emissions if not controlled. Relaxation of the roof rocks, ventilation pressure and the associated fracture connectivity allow gas to flow from all surrounding gas sources toward the mine workings, which eventually may create an unsafe condition for the underground workforce. |
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